Soy is a protein that comes from soybeans, soy yogurt, and tofu. It is often advised to eat soy in soybean form. It has been used to lower cholesterol, blood pressure, and blood fat levels. Soy has also been used to help control blood glucose and promote weight loss.
25 to 30 grams daily
Editorial process and description of evidence categories can be found at EBSCO NAT Editorial Process.
It is likely safe to take soy in small doses for a short time. Not enough studies have been done to say whether it is safe to take for a long period. Women who are pregnant or breastfeeding should avoid large amounts of soy.
Talk to your doctor about any supplements or therapy you would like to use. Some can interfere with treatment or make conditions worse.
A. Breast Cancer
A1. Van Patten CL, Olivotto CL, et al. Effect of soy phytoestrogens on hot flashes in postmenopausal women with breast cancer: a randomized, controlled clinical trial. J Clin Oncol. 2002;20(6):1449-1455.
B. Chronic Kidney Disease
B1. Zhang J, Liu J, et al. The effects of soy protein on chronic kidney disease: a meta-analysis of randomized controlled trials. Eur J Clin Nutr. 2014 Sep;68(9):987-993.
C1. Liu ZM, Chen YM, et al. Effects of soy intake on glycemic control: a meta-analysis of randomized controlled trials. Am J Clin Nutr. 2011;93(5):1092-1101.
C2. Yang B, Chen Y, et al. Systematic review and meta-analysis of soy products consumption in patients with type 2 diabetes mellitus. Asia Pac J Clin Nutr. 2011;20(4):593-602.
C3. Zhang XM, Zhang YB, et al. Soy Protein Supplementation Reduces Clinical Indices in Type 2 Diabetes and Metabolic Syndrome. Yonsei Med J. 2016;57(3):681-689.
D. Endocrine-Related Gynecological Cancers
D1. Myung SK, Ju W, et al. Soy intake and risk of endocrine-related gynaecological cancer: a meta-analysis. BJOG. 2009 Dec;116(13):1697-1705.
E. Endometrial Cancer
E1. Zhang GQ, Chen JL, et al. Soy Intake Is Associated With Lower Endometrial Cancer Risk: A Systematic Review and Meta-Analysis of Observational Studies. Medicine (Baltimore). 2015 Dec;94(50):e2281.
F. High Blood Pressure
F1. Dong JY, Tong X, et al. Effect of soya protein on blood pressure: a meta-analysis of randomised controlled trials. Br J Nutr. 2011;106(3):317-326.
F2. Liu XX, Li SH, et al. Effect of soy isoflavones on blood pressure: a meta-analysis of randomized controlled trials. Nutr Metab Cardiovasc Dis. 2012 Jun;22(6):463-470.
G. High Cholesterol
G1. Qin Y, Niu K, et al. Isoflavones for hypercholesterolaemia in adults. Cochrane Database Syst Rev. 2013 Jun 6;(6):CD009518.
G2. Malhotra A, Shafiq N, et al. Dietary interventions (plant sterols, stanols, omega-3 fatty acids, soy protein and dietary fibers) for familial hypercholesterolaemia. Cochrane Database Syst Rev. 2014;(6):CD001918.
H. Infantile Colic
H1. Gordon M, Biagioli E, et al. Dietary modifications for infantile colic. Cochrane Database Syst Rev. 2018 Oct 10;10:CD011029.
I. Lung Cancer
I1. Yang WS, Va P, et al. Soy intake is associated with lower lung cancer risk: results from a meta-analysis of epidemiologic studies. Am J Clin Nutr. 2011 Dec;94(6):1575-1583.
J1. Taku K, Melby MK, et al. Extracted or synthesized soybean isoflavones reduce menopausal hot flash frequency and severity: systematic review and meta-analysis of randomized controlled trials. Menopause. 2012 Jul;19(7):776-790.
J2. Zhang YB, Chen WH, et al. Soy isoflavone supplementation could reduce body weight and improve glucose metabolism in non-Asian postmenopausal women--a meta-analysis. Nutrition. 2013 Jan;29(1):8-14.
J3. Lethaby A, Marjoribanks J, et al. Phytoestrogens for menopausal vasomotor symptoms. Cochrane Database Syst Rev. 2013 Dec 10;(12):CD001395.
J4. Cheng PF, Chen JJ, et al. Do soy isoflavones improve cognitive function in postmenopausal women? A meta-analysis. Menopause. 2015 Feb;22(2):198-206.
J5. Franco OH, Chowdhury R, et al. Use of Plant-Based Therapies and Menopausal Symptoms: A Systematic Review and Meta-analysis. JAMA. 2016 Jun 21;315(23):2554-2563.
K1. Akhlaghi M, Zare M, et al. Effect of Soy and Soy Isoflavones on Obesity-Related Anthropometric Measures: A Systematic Review and Meta-analysis of Randomized Controlled Clinical Trials. Adv Nutr. 2017;8(5):705-717.
L. Prostate Cancer
L1. van Die MD, Bone KM, et al. Soy and soy isoflavones in prostate cancer: a systematic review and meta-analysis of randomized controlled trials. BJU Int. 2014 May;113(5b):E119-130.
Last reviewed July 2019 by EBSCO NAT Review Board Eric Hurwitz, DC Last Updated: 3/27/2020